Topic summary
US 20
Extracted from the Wikipedia article U.S. Route 20.
US 20 and US 30 break the general U.S. Route numbering rules in Oregon, since US 30 actually starts north of US 20 in Astoria, and runs parallel to the north throughout the state (the Columbia River and Interstate 84). The two run concurrently and continue in the correct positioning near Caldwell, Idaho. This is because US 20 was not a planned coast-to-coast route while US 30 was. US 20 originally ended at the eastern entrance of Yellowstone Park; it was extended in 1940.